Conversion rates rose as the number of keywords increased, peaking at between 33 to 38 percent when there were four keywords in total. Then rates dropped.

Single keywords searches had high conversion until company names were removed. Without these, single keyword searches then converted less than searches with two, three or
four terms in them.

Recommendations? If you aren't targeting longer phrases, you should be considering it. That's always been good advice, but this adds further backing to it. The flipside is
that longer terms generally bring in less traffic, something else the study confirmed.

More about the study, said to be based on mining traffic and conversation data for millions of records, can be found by reading the
white paper Oneupweb offers.

See also this past ClickZ article, Single-Word Searches Aren't Dead Yet, where Fredrick
Marckini recaps a similar study his firm iProspect did, looking at the number of terms used in searches over the years.